1. Field of the Invention
This invention relates to Group Transfer Polymerization and to selected silicon-based compounds which are useful as initiators therein.
2. Background
U.S. Pat. Nos. 4,414,372; 4,417,034; 4,508,880; 4,524,196; 4,581,428; 4,588,795; 4,645,716; 4,622,372; 4,656,233; 4,681,918; and 4,771,942, and and commonly assigned U.S. patent application Ser. No. 707,192 filed Mar. 1, 1985 and now abandoned, referred to hereinafter as "the aforesaid patents and patent applications", disclose processes for polymerizing a polar acrylic or maleimide monomer to a "living" polymer in the presence of an initiator, which is a tetracoordinate organosilicon, organotin or organogermanium compound having at least one initiating site, and a co-catalyst which is a source of bifluoride, fluoride, cyanide or azide ions or a suitable Lewis acid, Lewis base or selected oxyanion. Such polymerization processes have become known in the art as Group Transfer Polymerization (Webster et al. J. Am. Chem. Soc. 105, 5706 (1983)).
Preferred monomers for use in Group Transfer Polymerization are selected from acrylic and maleimide monomers of the formula CH.sub.2 .dbd.C(Y)X and ##STR1## and mixtures thereof, wherein:
X is --CN, --CH.dbd.CHC(O)X' or --C(O)X';
Y is --H, --CH.sub.3, --CN or --CO.sub.2 R, provided, however, when X is --CH.dbd.CHC(O)X', Y is --H or --CH.sub.3 ;
X' is --OSi(R.sup.1).sub.3, --R, --OR or --NR'R";
each R.sup.1, independently, is a hydrocarbyl radical which is an aliphatic, alicyclic, aromatic or mixed aliphatic-aromatic radical containing up to 20 carbon atoms or --H, provided that at least one R.sup.1 group is not --H; is:
(a) a hydrocarbyl radical which is an aliphatic, alicyclic, aromatic or mixed aliphatic-aromatic radical containing up to 20 carbon atoms; PA2 (b) a polymeric radical containing at least 20 carbon atoms; PA2 (c) a radical of (a) or (b) containing one or more ether oxygen atoms within aliphatic segments thereof; PA2 (d) a radical of (a), (b) or (c) containing one or more functional substituents that are unreactive under polymerizing conditions; or PA2 (e) a radical of (a), (b), (c) or (d) containing one or more reactive substituents of the formula --Z'(O)C--C(Y.sup.1).dbd.CH.sub.2 wherein Y.sup.1 is --H or --CH.sub.3 and Z' is O or NR' wherein R' is as defined below; and PA2 (a) a C.sub.1-12 alkyl, C.sub.4-12 cycloalkyl, C.sub.6-12 aralkyl or di(C.sub.1-4 alkyl)amino group; PA2 (b) a group of (a) wherein two or three of the alkyl, cycloalkyl and/or aralkyl groups are joined together by means of one or more carbon-carbon bonds; PA2 (c) a group of (a) or (b) wherein the alkyl, cycloalkyl and/or aralkyl groups contain within aliphatic segments thereof one or more hetero atoms selected from O, N and S; or PA2 a group of (a), (b) or (c) wherein the alkyl, cycloalkyl and/or aralkyl groups contain one or more substituents that are unreactive under polymerizing conditions; and
each of R' and R" is independently selected from C.sub.1-4 alkyl.
Preferred initiators are selected from tetracoordinate organsilicon, organotin and organogermanium compounds of the formulas (R.sup.1).sub.3 MZ, (R.sup.1).sub.2 M(Z.sup.1).sub.2 and O[M(R.sup.1).sub.2 Z.sup.1 ].sub.2 wherein:
R.sup.1 is as defined above for the monomer;
Z is an activating substituent selected from the group consisting of ##STR2## and mixtures thereof;
X', R', R", R and R.sup.1 are as defined above for the monomer;
each of R.sup.2 and R.sup.3 is independently selected from --H and hydrocarbyl, defined as for R above, subparagraphs (a), (c) and (d);
Z' is as defined above for the monomer;
m is 2, 3 or 4;
n is 3, 4 or 5;
Z.sup.1 is ##STR3## wherein X', R.sup.2 and R.sup.3 are as defined above;
at least one of any R, R.sup.2 and R.sup.3 in the initiator contains one or more initiating substituents of the formula --Z.sup.2 --M(R.sup.1).sub.3 wherein R.sup.1 is as defined above and M is as defined below;
Z.sup.2 is a diradical selected from the group consisting of ##STR4## and mixtures thereof, wherein R.sup.2, R.sup.3, X', Z', m and n are as defined above;
R.sup.2 and R.sup.3 taken together are ##STR5## provided, however, Z is ##STR6## and/or Z.sup.2 is ##STR7##
X' and either R.sup.2 or R.sup.3 taken together are ##STR8## provided, however, ##STR9## and
M is Si, Sn, or Ge, provided, however, Z is ##STR10## M is Sn or Ge, and provided, however, when Z.sup.2 is ##STR11## M is Sn or Ge.
Preferred co-catalysts are selected from a source of bifluoride ions HF.sub.2.sup.-, or a source of fluoride, cyanide or azide ions, or a source of oxyanions, said oxyanions being capable of forming a conjugate acid having a pKa (DMSO) of about 5 to about 24, preferably about 6 to about 21, more preferably 8 to 18, or a suitable Lewis acid, for example, zinc chloride, bromide or iodide, boron trifluoride, an alkylaluminum oxide or an alkylaluminum chloride, or a suitable Lewis base, for example, a Lewis base of the formula selected from (R.sup.4).sub.3 M' and ##STR12## wherein:
M' is P or As;
X.sup.1 is ##STR13## provided, however, when the monomer is a nitrile, X.sup.1 is ##STR14##
each R.sup.4, independently, is:
each R.sup.5 is --CH.sub.2 CH.sub.2 -- or --CH.sub.2 CH.sub.2 -- containing one or more alkyl or other substituents that are unreactive under polymerizing conditions.
Additional details regarding Group Transfer Polymerization can be obtained from the aforesaid patents and patent applications, the disclosures of which are hereby incorporated by reference.
The present invention provides additional silicon-containing initiators which can be used in Group Transfer Polymerization. The initiators of the present invention are unique for Group Transfer Polymerization, but they are not useful in prior known conventional processes for polymerizing the same type of monomer.
U.S. Pat. No. 4,491,669 discloses alkoxyaminosilanes of the formula R.sub.m Si(OR').sub.n (NR"R"').sub.p wherein R is H, short chain alkyl or aryl; R' is short chain alkyl or aryl; R" and R"' are separately H, short chain alkyl or aryl, at least one being other than H; m+n+p=4; and n and p are each at least 1.
U.S. Pat. No. 4,481,364 discloses silanes of the formula R.sup.1.sub.a SiH(OR).sub.3-a wherein R and R.sup.1 are, individually, monovalent C.sub.1-10 hydrocarbon radicals and a is 0, 1 or 2. Also disclosed are silanes of the above formula wherein H is replaced with a 3-aminopropyl group.
U.S. Pat. No. 4,310,640 discloses various silanes which contain the moiety X.sub.3-a Si(R.sup.1).sub.a --CH(R.sup.2)-- wherein R.sup.1 and R.sup.2 are H or C.sub.1-10 hydrocarbyl; X is halogen, alkoxy, phenoxyl, thioalkoxyl, aminooxyl, hydroxyl or amino; and a is 0, 1 or 2.
U.S. Pat. Nos. 4,251,650 and 4,430,504 disclose silyl ethers, useful as free radical polymerization initiators, which contain the moiety (R.sup.9)(R.sup.10)(R.sup.11)SiO--C--C-- wherein R.sup.9 can include methyl, ethyl, phenyl, benzyl, chloromethyl or a silicon-substituted 1,2-dioxyethyl moiety (A); R.sup.10 can include chloro, hydroxyl, methoxyl, ethoxyl or A; and R.sup.11 can include C1, OH or A.
U.S. Pat. No. 4,556,722 discloses a process for the preparation of aminopropylalkoxysilanes of the formula (R.sup.2)(R.sup.3)NCH.sub.2 CH(R.sup.4)CH.sub.2 Si(R.sub.a)(OR.sup.1).sub.3-a wherein R and R.sup.1 are alkyl, R.sup.2 and R.sup.3 are H, alkyl, alkenyl, aminoalkyl or phenyl, R.sup.4 is H or alkyl, and a is 0, 1 or 2 by reacting a silane of the formula (R.sub.a)HSi(OR.sup.1).sub.3-a with an alkenylamine.
U.S. Pat. No. 4,506,087 discloses the preparation of alkoxysilanes by reacting chlorosilanes of the formula (R.sub.a.sup.1)(R.sub.b.sup.2)SiCl.sub.4-a-b wherein the R groups are H or hydrocarbyl, a is 0 or 1-3 and b is 0 or 1, (a-b) being equal to or greater than 3, with alcohols.
U.S. Pat. No. 4,558,146 discloses the preparation of vinylaminosilanes of the formula R"'CH.dbd.CHSi(NRR').sub.x (R").sub.3-x wherein R' and R"', independently, are H or hydrocarbyl, R and R", independently, are hydrocarbyl, and x is an integer of 1-3, by reacting an aminosilane with an alkyne.
U.S. Pat. No. 4,579,965 discloses the preparation of vinyl tri-t-alkoxysilanes of the formula R"'CH.dbd.CHSi(OCRR'R").sub.3 wherein R"' is H or hydrocarbyl, and R, R' and R", independently, are hydrocarbyl, by reacting a tri-alkoxysilane with an alkyne in the presence of a platinum hydrosilation catalyst.
There is no suggestion in any of the aforesaid patents that such or similar silicon-containing compounds would be useful as initiators in Group Transfer Polymerization.